Electric motor controller



D. F. HASTINGS ELECTRIC MOTOR CONTROLLER March 19, 1940.

Filed March 3, 1939 INVENTOR Patented Mar. 19, 1940 PATENT oFr'rcE ELECTRIC MOTOR CONTROLLER Donald F. Hastings, Radburn, Fair Lawn, N. J.. assigner to Hardwick, Hindle, Inc., Newark,

Application March 3, 1939, Serial No. 259,510

Claims.

This invention relates to an electric motor controller and more especially to small motors such as are used on sewing machines where the speed of the motor is varied through manual operation l of the controller.

It is the principal object of my invention to provide a controller having a resistance unit of a simplified and improved construction, and one in which an adjustment is provided whereby the l movable contact member or contact lever may be interconnected with other operating parts of the controller, so that nearly the whole or only a fractional part of the resistance winding on the unit may be kept in circuit with the motor when u the controller is moved to the limit of its operating stroke.

Another object of my invention is to provide a motor controller made of a small number of parts in order to reduce the cost of manufacture.

Another object of my invention is to provide a resistance unit for a motor controller in which means are provided for opening or closing the motor circuit on a supplemental contact member rather than on the resistance per se. z5 These and other objects will be apparent to one skilled in this particular art, after reading the specification taken in connection with the annexed drawing, wherein:

Figure 1 is a part-sectional and part-elevational view through my improved form of controller.

Figure 2 is a bottom view of Figure 1 showing the movable contact member in the off position.

Figure 3 is a partial view of the unit shown in Figure 2 with the contact lever moved to its full on position.

Figure 4 is a View similar to Figure 1 but taken from the reverse side.

Figure 5 is a view similar to Figure 2 but showing the contact member in a certain position of 4D operation, the operating parts being adjusted so that the contact lever can only cut out a part of the resistance from the motor circuit.

In the various views, I is a casing having a pair of oppositely disposed ears 2 and 3 punched therefrom for pivotally supporting on the pin 4 a foot treadle 5. In some cases the treadle 5 has a pro jecting arm 6 so that when the casing I is placed Ys idewise on a sewing machine, the knee or some other part of the leg of the operator may engage the arm 5 to operate the treadle or lever 5. The treadle 5 is held in normal position by a spring I and the lever 5 is also provided with an arm 8 which projects through an orifice 9 in the top part of the casing I.

5s An insulator I0 is fastened to the interior of the casing by screws and nuts I I and I2, the nuts I2 being positioned in recesses I3 in the opposite ends of the insulator I U. Lock washers are preferably used under the nuts I2. The insulator IU is relatively fiat having a length and width such that it will readily fit within the interior ofthe casing I. The insulator is provided with two head portions I4 and I5, between which a winding of suitable resistance wire It is positioned. One end of the winding I@ is connected to a terminal post 10 Il' positioned on the head i4, andthe opposite end of the resistance winding terminates in a contact member Iii which is fastened to the head portion I5. As indicated in the drawing, the Contact member I8 is in the form of an eyelet 15 which may be readily anchored in a hole through the head I5 of the insulator IIl.

Extending longitudinally of the resistance unit is a strip I9 preferably of any satisfactory metal such as brass. The strip I9 is fastened to the 20 heads It and I5 of the insulator by studs 2t and 2 I, suitable nuts Z2 being used to clamp the strip in position. One of the studs, such as 29, may act as one terminal of the resistance unit.

Pivotally mounted as by a rivet Z3 to the strip 25 IS, is a Contact lever 2li. The lever 24 has a hole near the pivot 23 to receive a member 25 which is threaded at one end at 26 and has its opposite end Z'I bent over to pass through the said hole in the contact lever M. Preferably the extremity 2t of o0 the end El is swedged over to prevent the member 25 being readily withdrawn from the Contact lever 2t. The lever 24, preferably of a suitable metallic material, has a depressed portion or formation 29 made so as to engage only a small 35 number of turns on the winding I6. The end of the lever has a hole therein to receive the bent end Sii of a member 3| which is threaded at 32 in a reverse direction from the threads '.26 on the member 25.

Positioned between the members 25 and 32, and engaging the threaded ends thereof. is a member of suitable insulating material 33, which has right and left-hand threads therein to conform to the 45 threads 26 and 32, thereby forming a turnbuckle by which the connection between the operating lever arm Il and the contact lever 24 may be varied. As shown in Figure 5, adjustment is such that the lever arm 24 cannot be moved any 50 farther to the left, thus leaving a certain amount of resistance in series with the motor which will prevent excessive speed and vibration. There are some cases where such an arrangement is desirable, and I have found that the turnbuckle arrangement described is a very cheap and satisfactory means for attaining this object.

It may be stated that the insulator lil is slightly higher along the longitudinal line c-b shown in dotted lines. In other words, at the point where the winding iii is applied to the insulator lil, the insulator is slightly oval in shape. This means that the formation 29 on the Contact lever 24 will contact at various points along its length on the line arf- 19, but the circuit will be made and broken on the contact member I3, thereby preventing any arcing between the Contact lever 24 and the resistance wire, which is relatively small in diameter preferably being oxidized, with a suitable surface scraped free of the oxide along the line a--b and parts closely adjacent thereto.

The strip i9 is provided with notches 34 and 35 to allow for movement of the end 28 of the turnbuckle member 25, The notch 3d, together with the end 2li, may act as stop means to limit the oil movement of the arm 2li, and in some cases the end 23 and the notch may cooperate to form a stop for the contact lever in on position, although this is not necessary, as the lever 5 can engage the top of the housing l toaact as a stop in the on position of the controller.

While I prefer to make the strip lil out of metal, it may be made of suitable insulating material as long as an electrical connection is made between the end of the contact lever 2dand the terminal post 2li, but such changes may be made without departing from the spirit of my invention or the scope of the appended claims,

What I claim is:

lj. An electric motor controller including a casing and an operating lever mounted on the casing and having an arm extending within the casing, a resistance unit mounted within the casing and comprising an insulator having a continuous winding of resistance wire Wound thereon, a single, narrow metallic strip extending longitudinally of the insulator along one edge thereof and anchored at its ends to the insulator forming one terminal of the unit, second terminal carried directly by the insulator and having one end ci" the winding connected thereto, a Contact carried by the insulator adjacent one end of said strip and connected to the opposite end oi said winding and adapted to ce engaged by a contact lever, a contact lever pivoted to said strip near its center for contacting with said wire irst by way of said contact, and an adjustable link insulatingly connected between said lever arm and said contact lever.

2. An electric motor controller including a casing and an operating lever` mounted on the casing and having an arm extending within the casing, a resistance unit mounted within the casing and comprising an insulator having a continuous Winding of resistance wire wound thereon, a metallic strip extending longitudinally of the insulator along one edge thereof and anchored at its ends to the insulator and forming one terminal of the unit, a contact lever pivoted to said strip near its center for contacting with said wire, and a link connected between said lever arm and said contact lever, said link including two metallic parts having reversely threaded ends inter-connected by a turnbuckle of insulating material.

3. An electric motor controller including a casing and an operating lever mounted on the casing and having an arm extending within the casing, a resistance unit mounted within the casing and comprising, an insulator of a width somewhat less than the interior width of the casing to provide a relatively wide and nearly flat surface and a continuous winding of resistance wire on the insulator, terminals for the said unit, one of which is directly connected to the winding, a single narrow strip connected to the other terminal and extending along on one edge of the unit and having its other end anchored to the insulator, a contact carried by the insulator and connected to the other end of said winding, a Contact lever pivoted to Said strip and positioned to make and break a circuit through the winding by way of said contact and being in length sufcient to extend over a longitudinal median line through the unit, the free end of the contact lever being formed to make an extended engaging contact of considerable area in a transverse direction across the unit, various parts of said contact lever being brought successively into engagement with the winding along the centrally located line and narts closely adjacent thereto and an adjustable link insulatingly connected between said lever arm and said contact lever.

4. A resistance unit for an electric motor controllei` as set forth in claim l, further characterized in that said metallic strip has notches therein to provide clearance space for that end of the adjustable link which engages the contact member, one of the notches at least providing a stop means for the contact lever in "oil" position. f

5. An electric motor controller including a casing and an operating lever mounted. on the casing and having an arm extending within the casing, a resistance unit mounted within the casing and comprising an insulator having a continuous winding of resistance wire wound thereon, a metallic strip extending longitudinally of the insulator along one edge thereof and anchored at its ends to the insulator and forming one terminal of the unit, a contact lever pivoted to said strip near its center for contacting with said wire, and a link connected between said lever arm and said contact lever, said link including two metallic parts having reversely threaded ends inter-connected by a turnbuckle of insulating material, and a contact member acting as a terminal for one end of the winding, said contact member being positioned so that contact lever closes and opens the circuit through the winding at this contact member.

DONALD F. HASTINGS.' 

